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Tuesday January 31st

Tuesday January 31st . Friction, Air Resistance, And Terminal Velocity!. What will we learn today?. Content Objectives: S tudents will be able to compare amounts of friction in different scenarios

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Tuesday January 31st

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  1. Tuesday January 31st Friction, Air Resistance, And Terminal Velocity!

  2. What will we learn today? • Content Objectives:Students will be able to compare amounts of friction in different scenarios • Literacy Objective: Students will be able to definefriction as the force that opposesthe motion of two surfaces that are in contact

  3. Yesterday… • …we talked about forces,free-body diagrams, and balanced/unbalanced forces. • And one student (Gabe) brought up an interesting idea… • …if we drag this block across the table… isn’t there friction that slows it down?? So don’t we need to add that to our free-body diagram?

  4. Friction • Friction is the force that opposesthemotion of two surfaces that are in contact • The size of the frictional force depends on: • The materials the surfaces are made from (how rough they are) • The force pushing the two surfaces together (more force = more friction!)

  5. A Closer Look at Friction

  6. Three Types of Friction • Static Friction: frictional force that prevents two surfaces in contact from sliding past each other • (there is no movement! The objects are static, defined as “fixed or stationary”) Balanced Forces means NO MOVEMENT Man’s force Frictional force

  7. Static Friction • Static Friction increases as the downward force increases • More downward force = more contact between the two rough surfaces = more friction. • Let’s test it out!

  8. Three Types of Friction • Sliding Friction: frictional force that acts in the opposite direction to the motion of a surface sliding on another surface • This time, there IS movement • Smaller than force due to Static Friction Unbalanced Forces means A CHANGE in velocity = movement! Man’s force Frictional force

  9. Three types of Friction • Rolling Friction: frictional force that acts in the opposite direction to the motion of a surface ROLLING over another surface • Smallest frictional force (of the three type)

  10. Let’s take a look at how POWERFUL friction can be… • http://www.youtube.com/watch?v=jSu0Tvlm6LY • http://www.youtube.com/watch?v=hOt-D_ee-JE

  11. Friction lets us… • Walk on the ground without slipping! • Rock Climb! • Stop a moving car! • Hold a Pencil • Wear Glasses or sunglasseswithout them falling off

  12. A Special Type of Friction • Air Resistance is a type of friction that opposes the motion of objects that move through the air • Without Air Resistance, all objects would fall at the same rate of speed • Parachutes significantly increase air resistance, allowing for a safe landing for skydivers!

  13. Skydivers • Reach a terminal velocity of 120 mph when laying “flat” and 150-200 mph when diving head-first • Terminal Velocity is when air resistanceequals the accelerating force of gravity and the object cannot go any faster. • After the parachute is deployed, air resistance significantly increases and skydivers decelerate to a rate of 18mph

  14. Lets see Air Resistance in Action: • http://www.youtube.com/watch?v=1_fcX1YiWIU • Balanced Forces: http://www.youtube.com/watch?v=Ays6luaS4r0

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